<template>
  <div class="music-list">
    <div class="back" @click="go(-1)">
      <i class="icon-back"></i>
    </div>
    <h1 class="title">{{title}}</h1>
    <div class="bg-image" :style="bgImageStyle" ref="bgImage">
      <div
        class="play-btn-wrapper"
        :style="playBtnStyle"
      >
        <div
          v-show="songs.length > 0"
          class="play-btn"
          @click="random"
        >
          <i class="icon-play"></i>
          <span class="text">随机播放全部</span>
        </div>
      </div>
      <div class="filter" :style="filterStyle"></div>
    </div>
    <Scroll class="list" :style="scrollStyle" v-loading='loading' @scroll="onScroll" :probeType="3">
      <div class="song-list-wrapper">
        <Song-list :songs="songs" :rank="rank" @select="selectItem"></Song-list>
      </div>
    </Scroll>
  </div>
</template>

<script>
import Scroll from 'components/scroll/scroll'
// 歌曲列表封装
import SongList from 'components/base/song-list/song-list'
import { mapActions } from 'vuex'
export default {
  name: 'music-list',
  components: {
    Scroll,
    SongList
  },
  props: {
    songs: {
      type: Array,
      default: () => []
    },
    title: String,
    pic: String,
    loading: Boolean,
    noResultText: {
      type: String,
      default: '抱歉，没有找到可播放的歌曲'
    },
    rank: Boolean
  },
  data() {
    return {
      imageHeight: 0,
      scrollY: 0,
      // 最大滚动的距离
      maxTranslateY: 0
    }
  },
  computed: {
    bgImageStyle() {
      let zIndex = 0
      let paddingTop = '70%'
      let height = 0
      // 解决ios问题
      let translateZ = 0
      if (this.scrollY > this.maxTranslateY) {
        zIndex = 10
        paddingTop = 0
        height = '40px'
        translateZ = 1
      }
      let scale = 1
      // 下拉放大图片
      if (this.scrollY < 0) {
        scale = 1 + Math.abs(this.scrollY / this.imageHeight)
      }
      return {
        zIndex,
        paddingTop,
        height,
        transform: `scale(${scale}) translateZ(${translateZ}px)`,
        backgroundImage: `url(${this.pic})`
      }
    },
    scrollStyle() {
      return {
        top: `${this.imageHeight}px`
      }
    },
    // 上滑模糊
    filterStyle() {
      let blur = 0
      const scrollY = this.scrollY
      const imageHeight = this.imageHeight
      if (scrollY >= 0) {
        blur = Math.min(this.maxTranslateY / imageHeight, scrollY / imageHeight) * 20
      }
      return {
        backdropFilter: `blur(${blur}px)`
      }
    },
    playBtnStyle() {
      let display = ''
      if (this.scrollY >= this.maxTranslateY) {
        display = 'none'
      }
      return { display }
    }
  },
  mounted () {
    this.imageHeight = this.$refs.bgImage.clientHeight
    this.maxTranslateY = this.imageHeight - 40
  },
  methods: {
    go(val) {
      this.$router.go(val)
    },
    onScroll(val) {
      this.scrollY = -val.y
    },
    ...mapActions(['setLectPlay', 'randomPlay']),
    selectItem({ song, index }) {
      this.setLectPlay({
        list: this.songs,
        index
      })
    },
    random() {
      this.randomPlay(this.songs)
    }
  }
}
</script>

<style lang="scss" scoped>
  .music-list {
    position: relative;
    height: 100%;
    .back {
      position: absolute;
      top: 0;
      left: 6px;
      z-index: 20;
      transform: translateZ(2px);
      .icon-back {
        display: block;
        padding: 10px;
        font-size: $font-size-small-large-x;
        color: $color-theme;
      }
    }
    .title {
      position: absolute;
      top: 0;
      left: 10%;
      width: 80%;
      z-index: 20;
      transform: translateZ(2px);
      @include no-wrap();
      text-align: center;
      line-height: 40px;
      font-size: $font-size-small-large;
      color: $color-text;
    }
    .bg-image {
      position: relative;
      width: 100%;
      transform-origin: top;
      background-size: cover;

      .play-btn-wrapper {
        position: absolute;
        bottom: 20px;
        z-index: 10;
        width: 100%;
        .play-btn {
          box-sizing: border-box;
          width: 135px;
          padding: 7px 0;
          margin: 0 auto;
          text-align: center;
          border: 1px solid $color-theme;
          color: $color-theme;
          border-radius: 100px;
          font-size: 0;
        }
        .icon-play {
          display: inline-block;
          vertical-align: middle;
          margin-right: 6px;
          font-size: $font-size-small-medium-x;
        }
        .text {
          display: inline-block;
          vertical-align: middle;
          font-size: $font-size-small;
        }
      }
      .filter {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: rgba(7, 17, 27, 0.4);
      }
    }
    .list {
      position: absolute;
      bottom: 0;
      width: 100%;
      z-index: 0;
      .song-list-wrapper {
        padding: 20px 30px;
        background: $color-background;
      }
    }
  }
</style>
